Intruder first look: a promising tactical shooter that demands a thoughtful approach

Intruder reminds me of the golden age of Half-Life 1 modding: games like Action Half-Life, Science and Industry and Frontline Force, which experimented with the basic multiplayer FPS formula. It's a team-based stealth game where one group of players has to defend a pair of valuable briefcases from a squad of intruders. Everybody begins the game equipped with an assault rifle, a silenced pistol, satchel charges, proximity sensors, lockpicks, grenades and a camera that allows you to peek around corners. How you decide to use all of these tools to complete your objective is up to you.

Bullets are almost always lethal and being killed knocks you out for the entire round. Intruder encourages a sense of uncertainty, however, that makes it feel unlike any other online shooter I've played. There's no kill log, so your only way to confirm a kill is to find the body. Even then, you might be surprised: players can choose to 'ragdoll' their character at any time, and non-lethal wounds might leave a character prone but very much alive. This creates fascinating tension: I hit that guy, but is he dead? Can I shoot him again without attracting more attention?

Factor in full friendly fire and you'll see that Superboss Games have created something rare – a shooter where you really have to think before pulling the trigger. It's the work of Rob Storm and Austin Roush, who originally planned to create the game as a mod. The Unity engine has not only allowed them to create a standalone game, but also to invest that game with a level of detail that wouldn't otherwise be possible.

“If you make a mod, there's a strong chance that it's still going to feel like that original game in some way,” says Storm. “Intruder has its own feel because we built the controls and character movement from the ground up.”

Interacting with the game takes a bit of getting used to. Almost everything is affected by dynamic physics, from opening doors to the players themselves. Characters have a balance meter that reflects their stability – on flat ground you'll be fine, but leap onto a narrow balustrade and you're very likely to fall over. This injects a vein of slapstick that might seem at odds with Intruder's realistic tone, but it forces you to rethink the kind of actions that your character is capable of.

“Our entire approach to the game isn't making things larger, but making them deeper,” says Storm. “I think about what I would do in real life. I wouldn't just swing a door open – I'd open it a crack so I could see through it. We want to make people say, 'If I were really here, right now, what would I be doing?'”

Also key is the game's use of sound. Player microphones auto-transmit by default, and any noise you make is broadcast to anybody in earshot. If you talk too loudly, people will hear you. We're so used to seeing chat as something that exists outside of the game proper that the removal of reliable communication is a strangely isolating experience. If you need to talk to your teammates at range, you'll need to use a radio – and even then you are at risk of being heard by the enemy team.

During one match, I was playing as a guard when I heard gunshots from downstairs. I didn't know if one of my teammates had been shot, if we'd nailed an intruder, or if there'd been some kind of accident. Then I heard a voice from a nearby vent: one of the intruders, urgently radioing to find out what had happened to his compatriot. In that moment, I knew that the other team was just as confused as I was – and, crucially, I knew where at least one of them was.

The game is currently in paid alpha, and keys are released in batches of 500 to keep player numbers manageable. I didn't experience any stability issues but there are bugs, flat textures, and stiff animations. One of the advantages of being an early adopter, however, is a community that is currently very small and tight-knit. Most players respect the spirit of the game, which is crucial given how badly it could be broken by the use of external voice comms.

Storm acknowledges that cheating will always be an issue – but it's a risk that Superboss have to take in order to make an emergent multiplayer FPS. Private servers, coupled with the fact that the game is perfectly playable with small numbers of players, should ensure that the real experience remains available as the game expands its audience.

Keep an eye on this one. Intruder isn't ready for mass consumption just yet, but for a certain generation of FPS fan it has the potential to be something special.